<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        html,body{width: 100%;box-sizing: border-box;margin: 0px;}
        .span_close {border-radius: 65px;background-color: rgba(211, 56, 3, 0.64);position: absolute;font-size: 2px;width: 20px;height: 20px;box-sizing: border-box;padding-left: 6px;padding-top: 2px;cursor: pointer;top:3px;right: 3px;}
    </style>
</head>
<body>

<div style="position: relative;width: 100%;">
    <span class="span_close" title="关闭">X</span>
</div>

</body>
</html>